1. Field of the Invention
The present invention pertains to polishing machines, and in particular to machines for imparting a well-defined finish to one or more workpieces. The present invention is especially adapted to the double-sided precision polishing of computer hard drive memory storage disks.
2. Description of the Related Art
Machines have been made available for providing a very smooth, well-defined surface finish on workpieces, such as computer hard drive memory storage disks. Although single-sided polishing has been performed to a limited extent, the commercial emphasis today is on the double-sided machining of memory disks, such that both major surfaces of a disk structure can be utilized for memory storage, thus reducing the size of memory devices, while allowing greater memory capacities to be provided for a hard drive component of a given size. Over time, the magnetic density of memory storage disks has grown substantially, with an ever increasing number of data bits being stored on a surface area of given size. As a result, data storage bits have occupied increasingly smaller portions of a disk surface. Accordingly, the surface characteristics of memory disks have drawn increasing attention, with routine, extremely well-defined polishing of the memory disk surface being required.
In an attempt to improve hard drive access times and memory transfer rates, memory storage disks are being driven at higher speeds of disk rotation. Accordingly, overall (or so-called "global") dimensions and tolerances of memory storage disks are becoming increasingly important for improved hard drive performance. Further, as disk speeds increase, it becomes necessary to hold the transducers, commonly termed "magnetic heads" as close as possible to the surface of the memory disk to obtain usable signal strength. Thus, increasing demands are being made to reduce total run out of the memory storage disks and surface variations of memory storage disks are being more closely examined with a view toward reducing "high spots" of ever diminishing height. Further, in certain types of hard disk drive mechanisms, parallelism of the double-sided surfaces is becoming increasingly important for attainment of desired device performance.